One such system is known from U.S. patent application Ser. No. 165,276, filed on Feb. 5, 1987. The system described there for the open-loop control and/or closed-loop control of an internal combustion engine includes at least one measuring device for detecting an operating parameter of the internal combustion engine and/or of the motor vehicle in dependence upon which the internal combustion engine is open-loop controlled and/or closed-loop controlled. This operating parameter is especially the position of a power-determining element of an electronic accelerator pedal system such as a power actuator and/or an operator element actuable by the driver. A detection of a malfunction for the measuring device takes place starting from the signal values representing the operating parameter and supplied by the measuring device. The malfunction detection takes place by comparisons of these signal values to pregiven limit values in the form of a signal range check.
Difficulties then occur when the sensor utilized to detect an operating parameter of the engine and/or of the motor vehicle displays component ranges in its signal range which are characterized by a signal transmission or signal generation which is incomplete and adversely affected. This occurs for example because of contamination or when utilizing potentiometers since there poorly-conductive regions are formed on the resistance track because of abrasion in the component regions of its movement range and especially at the change-of direction points. These regions lead to a large contact resistance between the resistance track and the slider tap and therefore, on the one hand, lead to a false operating parameter signal value while, on the other hand, lead to a fault announcement in the monitoring system known from the state of the art and therefore to a failure of the system equipped with the measuring device.
The invention therefore has the object of providing measures which ensure an overall operational reliability and availability of the open-loop control system and/or closed-loop control system of an internal combustion engine. This is obtained in that a testing method is utilized for checking malfunctions of the measuring device detecting the operating parameter with the testing method being configured to be less sensitive within the pregiven component ranges than outside of these component ranges.
In a further embodiment, measuring devices can be provided which comprise several sensors which detect respective operating parameters of the internal combustion engine and/or of the motor vehicle especially the position of a power-determining element corresponding to the engine and/or vehicle. And, on the basis of the signal values generated by the sensors, a first malfunction check is carried out as to whether the signal values lie in a first pregiven value range and, in pregiven component ranges burdened with the above-mentioned problems (for potentiometers especially in idle regions or regions close to idle of the position of the particular element), a second malfunction check takes place as to whether the signal values individually and/or with respect to each other lie in a pregiven second value range.
A monitoring arrangement for an electronically controlled throttle flap in a motor vehicle is known from U.S. Pat. No. 4,603,675 with a measuring device being connected to the accelerator pedal of an electronic accelerator pedal system. In one of the embodiments, the measuring device comprises a position transducer potentiometer and a monitoring potentiometer. The position signal supplied by the position-transducer potentiometer is compared in a logic unit to threshold values determined from the signal of the monitoring potentiometer and the function of the measuring device is checked on the basis of the magnitude of the signal of the position-transducer potentiometer compared to the threshold values. This procedure likewise shows the above-mentioned disadvantages.